1. Field of the Invention
The present invention relates to an apparatus for manufacturing a luminous element substrate and a manufacturing method thereof, and more particularly, to an apparatus for manufacturing GaN substrate and a manufacturing method thereof.
2. Discussion of the Related Art
As demands on short-wavelength luminous elements of high efficiency are increased lately, a bluish-purple short-wavelength luminous element becomes a matter of great interest. Specifically, a blue light-emitting diode has a long luminous time and is widely applicable to various fields such as multimedia, information communication, and the like. Such a blue light-emitting diode generates a short-wavelength of about 450 nm, thereby enabling to improve a processing rate of an information processing system as well as increase an optical record density of an optical storage device greatly.
Generally, a blue light-emitting diode requires a GaN based compound for manufacture and uses a sapphire substrate. Yet, when a GAN layer is formed on the sapphire substrate, GaN differs from the sapphire substrate in lattice constant and heat expansion coefficient to generate crystalline defects of high density. Hence, the blue light-emitting diode needs a high threshold voltage.
In order to overcome such a problem, a GaN substrate, for which single crystalline GaN is grown, is tried to use as a substrate of a luminous element. Such a GaN substrate is manufactured by growing a thick GaN layer on a transparent sapphire substrate at a high temperature of at least 1,000° C., melting an interface between the GaN layer and the sapphire substrate using a laser beam through a lift-off process to separate a GaN substrate from the sapphire substrate.
However, the GaN substrate manufacturing method according to the related art carries out the laser lift-off process at a room temperature after growing the GaN layer at the high temperature of at least 1,000° C., whereby cracks are formed on the GaN substrate due to the abrupt temperature drop or the GaN substrate is bent.
Moreover, an apparatus for manufacturing the GaN substrate used for the method according to the related art is divided into one chamber for growing the GaN layer and the other chamber for the laser lift-off process, whereby the sapphire substrate having the GaN layer grown thereon may be broken while being transferred. Besides, the temperature difference between the two chambers brings about the crack or bending of the GaN substrate.